### question about assumption of inlet and outlet pressure in betz's law

Posted:

**Wed Oct 09, 2019 9:28 pm**Hi guys,

I have a question about assumption of inlet and outlet pressure in betz's law.

The upper diagram below is a control volume of one-dimensional air flow. The lower one is its pressure at corresponding places. Wind blows from left to right. And it is assumed air pressures at the far left and the far right are same as ambient pressure.

However, as far as I know, wind is caused by air pressure difference, so I am wondering if it is correct to assume that air pressure at these two far sides are same as ambient pressure (P1). If so, how could wind be caused?

Best,

Yanda

I have a question about assumption of inlet and outlet pressure in betz's law.

The upper diagram below is a control volume of one-dimensional air flow. The lower one is its pressure at corresponding places. Wind blows from left to right. And it is assumed air pressures at the far left and the far right are same as ambient pressure.

However, as far as I know, wind is caused by air pressure difference, so I am wondering if it is correct to assume that air pressure at these two far sides are same as ambient pressure (P1). If so, how could wind be caused?

Best,

Yanda